The invention relates to an automatic brake unit capable of operating a brake booster without the depression of a brake pedal, and more particularly, to an automatic operation detector which detects an operation of an automatic brake unit.
An automatic brake unit is known in the art which comprises a brake booster, a brake pedal which, when depressed, drives an input shaft of the brake booster to operate it, an automatic brake operating mechanism which operates the brake booster without the depression of the brake pedal, and a detection switch for detecting the operation of the brake booster without the depression of the brake pedal (Japanese Laid-Open Patent Application No. 86395/1997 and 127947/2000).
The detection switch is contained in a valve body of the brake booster. However, in order to allow the detection switch to be contained in the valve body, a redesign of passages and/or a change in the configuration of adjacent parts is required, presenting a difficulty in securing a space to contain the switch.
If a space can be secured to contain the detection switch, the space is very limited and thus requires a special design of a small size for the detection switch, resulting in an increased cost and an assembly which is less than desired.
In view of the foregoing, it is an object of the present invention to provide an automatic operation detector for an automatic brake unit which avoids a need for a special design of a small size for a detection switch and which allows a mounting space for the switch to be easily secured.
Specifically, in accordance with the present invention, there is provided an automatic brake unit comprising a brake booster, a brake pedal which, when depressed, drives an input shaft of the brake booster to operate it, an automatic brake operating mechanism which operates the brake booster without the depression of the brake pedal, and a detection switch for detecting the operation of the brake booster without the depression of the brake pedal;
the arrangement being such that the input shaft and the brake pedal are connected together in a manner to permit a relative displacement therebetween through at least an operating stroke of the detection switch, the detection switch being mounted on either the input shaft or the brake pedal so that when the brake pedal is depressed, the brake pedal is maintained at an advanced position with respect to the input shaft while the detection switch detects a retracting movement of the brake pedal with respect to the input shaft from the advanced position during an automatic brake operation.
With the described arrangement, the input shaft and the brake pedal are displaceable relative to each other through at least an operating stroke of the detection switch, which can then detect a retracting movement of the brake pedal with respect to the input shaft from the advanced position during an automatic brake operation.
On the other hand, during a normal brake operation, as the brake pedal is depressed, the brake pedal drives the input shaft forward. At this time, the brake pedal drives the input shaft forward while it is maintained at an advanced position with respect to the input shaft. Accordingly, this condition is not detected by the detection switch as an automatic brake operation.
Rather than containing the detection switch in a valve body of the brake booster, it can be mounted on either the input shaft or the brake pedal. Thus, a mounting space for the detection switch can be easily secured and no special design of a small size is required therefor, thus facilitating the mounting of the detection switch.
Above and other objects, features and advantages of the invention will become apparent from the following description of several embodiments thereof with reference to the drawings.